The present invention relates to a multiple control device for a linear actuator, and more particularly, to a control device that control the retractable member to be positioned at different positions by activating and stopping the DC motor.
A conventional linear actuator is shown in FIG. 1 and generally includes control device 10 which is connected with four limit switches 131, 132, 133 and 134 which are installed on the convention linear actuator 12. A retractable member 121 is retractably received in the actuator 12 and driven by a direct current (DC) motor 11. When the retractable member 121 is located in the deepest position as shown in FIG. 1, the electric power for the motor 11 is cut by the control device 10. When the motor 11 is activated by a signal sent from the control device 10, the retractable member 121 extends and the contact member 122 on the retractable member 121 removes from the first switch 131 and touches the second switch 132 which then sends a signal to the control device 10 to stop the motor 11 such that the retractable member 121 is set at the desired position. The same processes may proceed to let the retractable member 121 extend from the second switch 132 to the third switch 133 and the fourth switch 134. When the retractable member 121 is retracted from the position where the contact member 122 is engaged with the fourth switch 134, the control device 10 sends a reverse signal to the motor 11 which pulls the retractable member 121 backward and the retractable member 121 is stopped when the contact member 122 touches the third switch 133. By the process, the retractable member 121 can be retracted back to the original position. However, this requires a plurality of wires connected between the control device 10, the switches 131 to 134, and the motor 11. The wire connection could be a huge problem for multiple number of actuators in a building.
The present invention intends to provide a control device that includes a circuit which makes the connection between the actuator, the switches and the motor be simplified.
In accordance with one aspect of the present invention, there is provided a linear actuator which includes a casing and a retractable member driven by a motor is movably received in the casing and a contact member is connected to the retractable member. A first position switch connected to the motor, a plurality of travel switches and a final position switch are connected to the actuator. These switches are connected in series by normal-close switches. Normal-open switches of the travel switches located between the first position switch and the final position switch are connected to a circuit of the control device.
The primary object of the present invention is to provide a control device for a linear actuator wherein the circuit of the control device simplifies the wire connection between the position switches.
Another object of the present invention is to provide a control device wherein the position switches are connected in series so that the connection of the circuit is simplified even if the number of the position switches increases.